This will validate the current .html or .css file in Sublime Text 2. W3C's JSON CSS support is experimental so it isn't verbose, it will just tell you if you have errors. Not terribly helpful, but not sure how to augment that.

You must download the w3c-validator.py file separately from GitHub and throw it in your User directory, as well as validate.py below. Also, the curl command must be in the shell's PATH.

So while I'm running this, all I'm getting is errors...'retrying', 'retrying', 'failed'...is this still working? I've downloaded the two py files into User, and i'm running OSX, so curl is there--which I've confirmed by running curl http:// command to load one of my web pages...